The swan is Lelouch who tries to fly free from all bonds, however he can't manage to take off. The reason for this is CC, represented by the green (!!) nature around them (swans belong in the water), who really pulls all strings in the background and who gave him his current life, from which he wants to escape, since he's not happy at all (look at his face any time you see it).
He's not aware that in fact he's trying to escape from the green, because of the people chasing him, Suzaku, the thin man and behind him the emperor (the fat man) who gives the orders.
Thin Suzaku is convinced to get him, the outstrechted arms prove that, however there is a too big distance betwenn them (which represents their broken friendship), he can't grasp him. On the other hand he doesn't really want to (look at his legs), since he still has secret feelings for him and don't want to give him to the emperor.
The emperor is the fat man with the stick, which represents his scepter and the round hat, which represents a crown. His fatness shows, that he is a man who doesn't need to move fast or do heavy work, he's mainly there to think and give orders. He is just a little pissed, because Suzaku holds back traing to catch Lelouch, the swan.